Key words Piezoelectric material, electro-elastic constitutive law, C0 semigroup of linear continuous operators, infinitesimal generator, fully discrete scheme, finite element method, convergence, error estimation, numerical simulation.We study a dynamic problem for linearly electro-elastic materials, permitting piezoelectric effects. As a theoretical result, we state and prove the existence of a unique solution to the problem by using arguments of semi-linear evolutionary equations and semigroups of linear continuous operators. Then we introduce a fully discrete scheme to solve the problem numerically. Under certain solution regularity assumptions, we derive an optimal order error estimate. Finally, we present some numerical results on a two-dimensional test problem to illustrate the theoretical error estimate.